The present invention relates to an electrical switch. More specifically, the invention is concerned with a reliable display of switching position, even in the case of malfunction, of an electrical switch, particularly a motor protection switch, in which actuation of the movable contacts is effected by a switch latch operated by an "on" button and an "off" button and in which the "on" button is intended to display the switch position.
In previously employed motor protection switches, an unequivocal "off" position was not always assured if, for example, the contacts were welded together due to overheating from excessive current, and the like. If in these devices the motor switch is turned off but the contacts are welded together, the "on" button usually moves outwardly a sufficient distance such that an error can be noted only by a very close inspection.
German Printed Application DE-PS No. 2,705,330 discloses an electrical switch in which a rocker is disposed outside the side plates of the switch latch. This rocker is arranged to block the "on" button of the switch until a drive lever which actuates the contact member carrier has moved to such an extent that a change in position of the angular lever can take place and the rocker releases the "on" button of the switch.
German Laid-Open Application DE-OS No. 3,213,493 discloses an electrical switch in which an "on" button is latched in a similar manner within the side plates of the switch latch by use of a blocking slide actuated by a compression spring. When deactivating the switch, the drive lever of the contact member carrier actuates the blocking slide. After a certain path length, the latter releases the "on" button.
In both embodiments, the blocking member is released by a drive lever whose path is much shorter at the point of engagement than the path of the movable contacts. This results in a great susceptibility to tolerances.